Russian President Vladimir Putin loomed over the catastrophe of a downed Malaysia Airlines passenger jet from the start Thursday, as Russian news agencies reported that he was the first to inform President Obama of the crash and he quickly placed blame on his adversaries in the Ukrainian government.

“Obviously, the state over which this incident took place is responsible for this terrible tragedy,” Mr. Putin said, according to ITAR-Tass, a Russian news agency. “This tragedy would have never happened should this land was peaceful, if combat operation had not been resumed in Ukraine’s southeastern regions.”

Mr. Putin moved quickly to carve out a role for himself and his country. Russia asked for its investigators to be granted access to the crash site.

Russian news agencies reported that Ukrainian separatists fighting the Kiev government said they would turn over the plane’s data recorders to Moscow, which they argued has better tools to analyze the disaster.

The Malaysia AirlinesBoeing 777 with 298 passengers and crew members aboard went down near the city of Donetsk, a pro-Russia stronghold in eastern Ukraine that has been the scene of pitched battles in recent days between separatists and the Ukrainian military.

Each side in the conflict accused the other of shooting down the plane with a surface-to-air missile. U.S. news reports said American officials confirmed a missile attack and later reported that U.S. intelligence had ruled out Ukraine as the culprit.

Russian press accounts, meanwhile, immediately fingered Ukraine. They quoted sources who said the rebel forces didn’t have the kind of hardware required to shoot down the jetliner.

“We are being accused almost every day, with Kiev promising to provide ‘undeniable evidence’ as soon as possible. However, this ‘evidence’ tends to disappear without a trace, and they try to cover up the embarrassment with new and even more bizarre accusations,” a high-ranking military official among the rebels told RIA Novosti.

The news agency also cited an “expert source” who said the Ukrainian army battalion of Buk air defense systems was deployed in the vicinity of the crash a day earlier, “making the downing of the aircraft by one of the missiles highly probable.”

Tensions between Russia and the West reached a boiling point after Russia annexed the Crimean Peninsula, formerly a portion of Ukraine, and moved troops to the Ukrainian border.

The Obama administration has responded with several rounds of sanctions, including a series Wednesday. It was the imposition of those sanctions that initiated the phone call Thursday between Mr. Putin and Mr. Obama.

The White House said Mr. Putin requested the call and that Mr. Obama sternly told Mr. Putin that his actions would determine whether sanctions are eased or toughened.

“The president’s made clear that the international community, the United States and our European allies are willing to take steps and impose economic costs on Russia if they decline to respect those basic norms,” White House press secretary Josh Earnest told reporters traveling with the president aboard Air Force One.

It was near the end of the call when Mr. Putin raised early reports of the downed passenger jet, Mr. Earnest said.

Russian news agencies emphasized that the airliner went down about 31 miles from the Russian border inside Ukraine and took pains to quote Russian officials who said Ukraine was responsible for flight safety in the area of the crash.

There have been several disputes over planes being shot down over eastern Ukraine in recent days.

On Wednesday evening, a Ukrainian fighter jet was shot down by an air-to-air missile from a Russian plane, Ukrainian authorities said Thursday, adding to what Kiev says is mounting evidence that Moscow is directly supporting the separatist insurgents.

Ukrainian Security and Defense Council spokesman Andrei Lysenko said the pilot of the Sukhoi-25 jet hit by the air-to-air missile was forced to eject as his jet was shot down.

Russia’s U.N. Ambassador Vitaly Churkin told reporters at U.N. headquarters in New York that Russia did not shoot down the Ukrainian fighter jet Wednesday.

Pro-Russia rebels also claimed responsibility for strikes Wednesday against two Ukrainian Sukhoi-25 jets.

Meanwhile, leaders of the separatist militia known as the Donetsk People’s Republic said they could not rule out Ukrainian servicemen in the downing of the Malaysia AirlinesBoeing 777.

“Very serious clashes are ongoing in the region where the Boeing crashed. Nonstop gunfire is under way there,” Andrei Purgin, the militia’s first deputy prime minister, told Interfax.

Almost immediately after the crash, Moscow asked for its investigators to be granted access to the crash site, which is controlled by the Russia-backed separatists in the region who reportedly blocked access by Ukraine authorities.